1. Field of the Invention
This invention relates to an ophthalmologic apparatus having a plurality of measuring and examining functions requiring different working distances, such as measuring the cornea refractive power and measuring the eye axis length.
2. Related Background Art
Heretofore, a spectacle lens or a contact lens has been used to correct the refractive power of the eye after a surgical cataract operation, but in recent years, it has been practised to insert an in-the-eye lens into the position of the removed crystalline lens. To choose a proper in-the-eye lens for a patient having an eye without a crystalline lens, it is necessary to know the cornea refractive power and the eye axis length, i.e., the length from the cornea to the retina.
In the past, however, there has been the inconvenience that the measurement of the cornea refractive power is effected by a cornea shape measuring apparatus and the measurement of the eye axis length is effected by a discrete ultrasonic measuring apparatus, from which the refractive power of the in-the-eye lens must be calculated.
An apparatus having the both functions is proposed in U.S. application Ser. No. 906,271 now U.S. Pat. No. 4,764,006. In this case, it is desired that during the measurement of the shape of the cornea, the corneal reflection image not be eclipsed by the image of an eye axis length measuring probe which is present in the optical path.
It is also desirable to eliminate the necessity that the system for measuring the eye axis length be optically transparent.
Further, an apparatus in which a slidable bed need not be moved in a horizontal plane is desirable because an attempt to effect two measurements by moving the slidable bed in a horizontal plane in the direction of the optic axis results in the destruction of the alignment in a direction perpendicular to the optic axis.
U.S. application Ser. No. 162,250 now abandoned has been proposed as an apparatus which satisfies these requirements, but it is desired that consideration be given to the safety of the cornea of an eye to be examined when an eye axis length measuring probe (a detecting terminal) is brought close to the cornea of the eye to be examined by driving means.